package com.imooc.ecommerce.filter;

import com.alibaba.fastjson.JSON;
import com.imooc.ecommerce.constant.CommonConstant;
import com.imooc.ecommerce.constant.GatewayConstant;
import com.imooc.ecommerce.util.TokenParseUtil;
import com.imooc.ecommerce.vo.JwtToken;
import com.imooc.ecommerce.vo.LoginUserInfo;
import com.imooc.ecommerce.vo.UsernameAndPassword;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.Ordered;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.nio.CharBuffer;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.atomic.AtomicReference;

/**
 * 全局鉴权过滤器
 *
 * @author zhangshao
 * @since  2023/11/25 9:35
 */
@Slf4j
@Component
public class GlobalLoginOrRegisterFilter implements GlobalFilter, Ordered {

    /**
     * 注册中心客户端，可以从注册中心获取服务实例信息
     */
    private final LoadBalancerClient loadBalancerClient;

    private final RestTemplate restTemplate;

    public GlobalLoginOrRegisterFilter(LoadBalancerClient loadBalancerClient, RestTemplate restTemplate) {
        this.loadBalancerClient = loadBalancerClient;
        this.restTemplate = restTemplate;
    }

    /**
     * 登录、注册、鉴权
     * 1. 如果是登录或注册，则去授权中心拿到token,并返回给客户端
     * 2. 如果是访问其他服务，则鉴权，没有权限，返回 401
     *
     * @param exchange
     * @param chain
     * @return
     */
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ServerHttpRequest request = exchange.getRequest();
        ServerHttpResponse response = exchange.getResponse();
        if (request.getURI().getPath().contains(GatewayConstant.LOGIN_URI)) {
            //去授权中心拿token
            String token = getTokenFromAuthorityCenter(request, GatewayConstant.AUTHORITY_CENTER_TOKEN_URL_FORMAT);
            //Header中不能设置null
            response.getHeaders().add(CommonConstant.JWT_USER_INFO_KEY,
                    null == token ? "null": token);
            response.setStatusCode(HttpStatus.OK);
            return response.setComplete();
        }
        //如果是注册
        if (request.getURI().getPath().contains(GatewayConstant.REGISTER_URI)) {
            //去授权中心拿token,先创建用户，在返回token
            String token = getTokenFromAuthorityCenter(request, GatewayConstant.AUTHORITY_CENTER_REGISTER_URL_FORMAT);
            response.getHeaders().add(
                    CommonConstant.JWT_USER_INFO_KEY,
                    null == token ? "null" : token
            );
            response.setStatusCode(HttpStatus.OK);
            return response.setComplete();
        }

        //3. 访问其他服务,则鉴权,校验是否能从token中解析用户信息
        HttpHeaders headers = request.getHeaders();
        String token = headers.getFirst(CommonConstant.JWT_USER_INFO_KEY);
        LoginUserInfo loginUserInfo = null;
        try{
            loginUserInfo = TokenParseUtil.parseUserInfoFromToken(token);
        }catch (Exception ex){
            log.error("parse user info from token error :[{}]",ex.getMessage(),ex);
        }

        //获取不到登录用户信息,返回401
        if(null == loginUserInfo){
            response.setStatusCode(HttpStatus.UNAUTHORIZED);
            return response.setComplete();
        }

        //解析通过,则放行
        return chain.filter(exchange);
    }

    @Override
    public int getOrder() {
        return HIGHEST_PRECEDENCE + 2;
    }

    /**
     * 从授权中心获取token
     *
     * @param request
     * @param uriFormat
     * @return
     */
    private String getTokenFromAuthorityCenter(ServerHttpRequest request, String uriFormat) {

        //service id 就是服务名字,负载均衡
        ServiceInstance serviceInstance = loadBalancerClient.choose(

                CommonConstant.AUTHORITY_CENTER_SERVICE_ID

        );
        log.info("Nacos Client Info :[{}],[{}],[{}]", serviceInstance.getServiceId(), serviceInstance.getInstanceId(), JSON.toJSONString(serviceInstance.getMetadata()));
        String requestUrl = String.format(
                uriFormat, serviceInstance.getHost(), serviceInstance.getPort()
        );
        UsernameAndPassword requestBody = JSON.parseObject(
                parseBodyFromRequest(request), UsernameAndPassword.class
        );
        log.info("login request url and body :[{}],[{}]", requestUrl, JSON.toJSONString(requestBody));
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        JwtToken token = restTemplate.postForObject(
                requestUrl, new HttpEntity<>(JSON.toJSONString(requestBody), headers), JwtToken.class
        );
        if (null != token) {
            return token.getToken();
        }
        return null;
    }

    /**
     * 从post请求中获取到请求数据
     *
     * @param request
     * @return
     */
    private String parseBodyFromRequest(ServerHttpRequest request) {

        //获取请求体
        Flux<DataBuffer> body = request.getBody();
        AtomicReference<String> bodyRef = new AtomicReference<>();

        //订阅缓冲区去消费请求体中的数据
        body.subscribe(buffer -> {
            CharBuffer charBuffer = StandardCharsets.UTF_8.decode(buffer.asByteBuffer());
            //一定要使用DataBufferUtils.release释放掉，否则会出现内存泄漏
            DataBufferUtils.release(buffer);
            bodyRef.set(charBuffer.toString());
        });

        //获取请求体中的数据
        return bodyRef.get();
    }
}
